[Xen-devel] [PATCH 12/18] xen/arm: Introduce new helpers to handle guest/hyp SErrors

[Wei Chen <Wei.Chen@xxxxxxx>]

Currently, ARM32 and ARM64 has different SError exception handlers.
These handlers include lots of code to check SError handle options
and code to distinguish guest-generated SErrors from hypervisor
SErrors.

The new helpers: do_trap_guest_serror and do_trap_hyp_serror are
wrappers of __do_trap_serror with constant guest/hyp parameters.
__do_trap_serror moves the option checking code and SError checking
code from assembly to C source. This will make the code become more
readable and avoid placing check code in too many places.

These two helpers only handle the following 3 types of SErrors:
1) Guest-generated SError and had been delivered in EL1 and then
   been forwarded to EL2.
2) Guest-generated SError but hadn't been delivered in EL1 before
   trapping to EL2. This SError would be caught in EL2 as soon as
   we just unmasked the PSTATE.A bit.
3) Hypervisor generated native SError, that would be a bug.

In the new helpers, we have used the function "inject_vabt_exception"
which was disabled by "#if 0" before. Now, we can remove the "#if 0"
to make this function to be available.

Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx>
---
 xen/arch/arm/traps.c            | 69 +++++++++++++++++++++++++++++++++++++++--
 xen/include/asm-arm/processor.h |  4 +++
 2 files changed, 71 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 053b7fc..48cfc8e 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -646,7 +646,6 @@ static void inject_dabt_exception(struct cpu_user_regs 
*regs,
 #endif
 }
 
-#if 0
 /* Inject a virtual Abort/SError into the guest. */
 static void inject_vabt_exception(struct cpu_user_regs *regs)
 {
@@ -676,7 +675,59 @@ static void inject_vabt_exception(struct cpu_user_regs 
*regs)
 
     current->arch.hcr_el2 |= HCR_VA;
 }
-#endif
+
+/*
+ * SError exception handler. We only handle the following 3 types of SErrors:
+ * 1) Guest-generated SError and had been delivered in EL1 and then
+ *    been forwarded to EL2.
+ * 2) Guest-generated SError but hadn't been delivered in EL1 before
+ *    trapping to EL2. This SError would be caught in EL2 as soon as
+ *    we just unmasked the PSTATE.A bit.
+ * 3) Hypervisor generated native SError, that would be a bug.
+ *
+ * A true parameter "guest" means that the SError is type#1 or type#2.
+ */
+static void __do_trap_serror(struct cpu_user_regs *regs, bool guest)
+{
+    /*
+     * Only "DIVERSE" option needs to distinguish the guest-generated SErrors
+     * from hypervisor SErrors.
+     */
+    if ( serrors_op == SERRORS_DIVERSE )
+    {
+        /* Forward the type#1 and type#2 SErrors to guests. */
+        if ( guest )
+            return inject_vabt_exception(regs);
+
+        /* Type#3 SErrors will panic the whole system */
+        goto crash_system;
+    }
+
+    /*
+     * The "FORWARD" option will forward all SErrors to the guests, except
+     * idle domain generated SErrors.
+     */
+    if ( serrors_op == SERRORS_FORWARD )
+    {
+        /*
+         * Because the idle domain doesn't have the ability to handle the
+         * SErrors, we have to crash the whole system while we get a SError
+         * generated by idle domain.
+         */
+        if ( is_idle_vcpu(current) )
+            goto crash_system;
+
+        return inject_vabt_exception(regs);
+    }
+
+crash_system:
+    /* Three possibilities to crash the whole system:
+     * 1) "DIVERSE" option with Hypervisor generated SErrors.
+     * 2) "FORWARD" option with Idle Domain generated SErrors.
+     * 3) "PANIC" option with all SErrors.
+     */
+    do_unexpected_trap("SError", regs);
+}
 
 struct reg_ctxt {
     /* Guest-side state */
@@ -2863,6 +2914,20 @@ asmlinkage void do_trap_guest_error(struct cpu_user_regs 
*regs)
     domain_crash_synchronous();
 }
 
+asmlinkage void do_trap_hyp_serror(struct cpu_user_regs *regs)
+{
+    enter_hypervisor_head(regs);
+
+    __do_trap_serror(regs, VABORT_GEN_BY_GUEST(regs));
+}
+
+asmlinkage void do_trap_guest_serror(struct cpu_user_regs *regs)
+{
+    enter_hypervisor_head(regs);
+
+    __do_trap_serror(regs, true);
+}
+
 asmlinkage void do_trap_irq(struct cpu_user_regs *regs)
 {
     enter_hypervisor_head(regs);
diff --git a/xen/include/asm-arm/processor.h b/xen/include/asm-arm/processor.h
index 148cc6f..885dbca 100644
--- a/xen/include/asm-arm/processor.h
+++ b/xen/include/asm-arm/processor.h
@@ -709,6 +709,10 @@ int call_smc(register_t function_id, register_t arg0, 
register_t arg1,
 
 void do_trap_guest_error(struct cpu_user_regs *regs);
 
+void do_trap_hyp_serror(struct cpu_user_regs *regs);
+
+void do_trap_guest_serror(struct cpu_user_regs *regs);
+
 /* Functions for pending virtual abort checking window. */
 void abort_guest_exit_start(void);
 void abort_guest_exit_end(void);
-- 
2.7.4


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